Mass production of resistors



y 1963 J. G. RUCKELSHAUS 3,095,636

MASS PRODUCTION OF RESISTORS Filed July 17, 1959 FIG. 2

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INVENTOR. JOHN G. RUCKELSHAUS FIG? FIG.5

HIS ATTORN EY Unite taes atent enemas MASS PRODUCTION F RESISTORS John G. Ruckelshaus, 110 Pomeroy Road, Madison, NJ. Filed July 17, 1959, Ser. No. 827,937 3 Claims. c1. 29-15562) This invention relates to a method of making resistors, and more particularly relates to the mass production of film resistors at a relatively low cost.

This is a continuation in part of my copending application, Serial No. 292,367, filed June 7, 1952 now U.S. Patent No. 2,917,814 dated December 22, 1959.

In my above noted applications, I have indicated various methods and techniques of preparing resistors of various types of which relates to a method of making a single resistor, by utilizing a vacuum apparatus and inserting a tube or plate into the center of said vacuum apparatus, outgassing the vacuum chamber and contents evacuating and passing a filament proximate the surface of the tube or plate to be coated and producing a vacuum in the chamber of the apparatus and finally heating the filament to such an extent that the metal forming the filament evaporates or sublimates and passes on to the proximate surface of the tube or plate. In connection with the present invention as disclosed herein, it is intended to manufacture the above noted resistor on a large scale or on a mass production basis so as to reduce the cost of the individual resistors produced.

With the above and other features in View, it is an object of the present invention .to provide a method of making resistors on a mass production basis at a relatively low or economic cost.

One other object of the present invention is to provide a method of making metal film resistors wherein blanks may be made in bulk, and the individual resultant resistors may be adjusted to the required values as desired.

A further object of the present invention is to provide resistor units made on a mass production basis, each of said units being stable and having a lower temperature coefiicient of resistance than previously used resistors of deposited carbon film types.

Still another object of the present invention is to provide a simple, low cost precision metal type film resistor units made on a large scale basis.

Still another object of the present invention is to provide a method of coating a non-conducting member, with a film of conductive material on a mass production basis, the thickness of the coating depending on the desired electrical resistance, and then sealing the ends of each of the individual units and connecting the ends with conductors.

A more specific object of the present invention is to provide a method of making a metal film resistor in quantity and on mass production basis wherein dielectric members are inserted in a large bell jar, said members being mounted on jigs or fixtures and a metal electroconductor filament is run through the jar and adjacent the members, the members and filament and fixtures are outgassed, and the filament is heated While the jar is under high vacuum so that a met-allized surface is obtained in each of the resistor units preparatory to final treatment.

Another specific object of the present invention is to provide a method of treating dielectric members under conditions of high vacuum and at a high temperature in the presence of at least one metal electroconductive filament whereby the filament is heated and vaporized and the resultant vapors pass on to the adjacent dielectric members to coat the same, and then subjecting the product to further regulatory treatment to form a resistor of desired temperature coefiicient.

Other objects and features of my invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a sectional view of a preferred assembly showing tubular or cylindrical dielectric members used and treated in accordance with my invention;

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1 showing an enlarged detail of the embodiment illustrated therein;

FIG. 3 is a sectional View showing the assembly of jigs mounted in a vacuum chamber;

*FIG. 4 is a top plan view of another modification showing the flat type of resist-or.

FIG. 5 is a face view partly broken away of a portion of the assembly shown in FIG. 4;

FIG. 6 is a top plan detail view of FIG. 5.

FIG. 7 is a vertical face view showing modified resistor plates and holder; and

FIG. 8 is a top plan view of FIG. 7.

Referring now to the drawings in which similar reference numerals denote like parts throughout, it will be noted according to my invention that I provide two types of resistors, first a tubular or cylindrical type, and sec ondly a flat or plate type of resistor. Said members are made of any dielectric material, glazed or unglazed, such as glass, porcelain, Alundum and the like ceramic material on to which a metal film can be evaporated or sublimated.

Referring specifically to FIGS. 1, 2 and 3, it will be noted that in treating cylindrical members to form a resistor, there is provided a fixture 10 having a plurality of supporting members or rods 11, such as of stainless steel or similar material. Said members are equispaced around a common center and are adapted at both ends thereof to be retained by removable top and bottom mica plates 12 and 13 respectively as shown in FIG. 1, thereby forming a support frame. The purpose of said upright support rods 11 is to accommodate tubes or cylinders 14 which are laid end to end in tandem within the area defined by the rods 11 between the mica plates 12 and 13. Each of said tubes 14 is kept separate and apart from each other by individual intermediate spacer members 15 to provide spaces 16 and to permit any occluded or other gases to escape from the interior of the tubes 14 during the outgassing and final heating and vacuum operations. Said spacers comprise annuli with spacer pins on the top and bottom thereof vertically disposed so that there is sufiicient space between each tube to allow free removal of the outgas.

Each of the tubes 14- is provided with end terminals of a highly conductive metal such as platinum or silver at least on the interior ends thereof preparatory to their use in the present process.

The individual tubes and spacers when arranged in tandem as shown between the three support rods 11 to form the arrangement as shown in FIG. 1, are then provided with a filament 17 which extends axially thru the tubes and spacers. Said filament is composed of pure alloy metals such as Nichrome or similar alloy so that when it is heated in vacuo at high temperatures and low pressures it sublimates onto the proximate surface of the tubes. Said filament 17 is adapted to pass through the stacks and has its upper end 18 connected to a conductor support 19 having a vertical conductor support arm 20 which is fixed to the base 21 of vacuum chamber apparatus 22. The top and bottom mica piece or sheet 12 or 13 is readily placed over the rods 11 and held there in position by means of suitable washer members 23. The resultant assembly is then placed into vacuum chamber 22. The filament 17 is then connected to a source of variable electrical power, not shown. It is to be noted that the filament extending through the center of the tubes aosaeae '2 2.9 is secured at the support 19 so as to prevent sagging of the filament when it is subjected to heat and high electrical current. Upon passing current through said filament, it evaporates or sublimates from the filament onto the interior wall of the cylinders or tubes.

Once the assembled unit has been placed in the vacuum chamber 22a of apparatus 22 the air is removed from the chamber and a vacuum of at least mm. of Hg is created in the vacuum chamber. It is intended to outgas the materials present in the assembled unit. The filaments 17 are then heated to a temperature under sublimation temperature to outgas the interior of the apparatus 22 and the contents. The bell jar is also heated externally to further permit outgassing within said vacuum chamber.

After the outgassing operation is completed, the filament is then heated to a sublimation temperature where the alloy from the filament deposits on the inner wall of the tubes and the metallic fired terminals in each cylinder. The filament is heated for a period of 5 minutes to 5 hours at a temperature of 150 C. to 450 C. It is to be noted that the length of time the filament is heated to the subliming temperature determines the amount of the deposit on the tubes and the resistance value of the resultant product. The longer the heating the lower the resistance of the final unit.

After this operation has been completed, the tubes within the Whole fixture are removed from the bell jar and heat treated at an elevated temperature anywhere from 120 to 200 degrees C. in air for a period of at least 0.55 hour to stabilize them.

The tubes are then removed from the assembly and are then sorted in an auto bridge and then individually adjusted by either grinding the tops of the threads if the tube is internally threaded before sublimation or by grinding, milling, cutting or otherwise forming a helical resistance path on the inner wall of the tube if its well is smooth to a desired resistance value. The tubes are then capped and coated by either spraying molding or dipping in a resin so as to produce a highly sealed resistance unit forming a finished product. It can readily be seen from the foregoing that many tubular members can be strung onto one fixture, and said filament 17 heated or lighted so as to create several resistors at a time. These resistors can be removed from the apparatus 22 and terminals attached, thus economically forming a stable metal film resister of extremely low temperature co-efiicient of resistance. In present type of tubes the ends can be filled with a casting material, in order to seal the resistance element. Furthermore, the ends of the cylinder are initially provided with end terminals baked thereon, namely on the inside, the ends and the outside so that an end cap can be readily added thereon. By manufacturing a resistor of this type, care must be taken to produce a resistance film that is stable and one that has a low temperature coefficient of resistance.

With regard to the modification shown in FIGS. 4 to 6, it will be noted that there is shown an assembly for batch process operation in which flat plate resistors can be made. Flat plates 24 of dielectric material are mounted on a fixture 25 which fixtures may be arranged in any suitable manner in bell jar 22. The fixture 25 consists of a back plate 26 having internally bent opposed end portions 27 and 23 forming channels 28a and 28b to accommodate a stack of said plates 24 arranged in tandem. Said tracks 27 and 28 support the plates 24 so that only one side of said material is exposed to the evaporation action of the high alloy filament. It is to be noted that the plates 24 are kept separate and apart from each other by means of spacer members 29 so as to permit outgassing of the interior of the vacuum chamber and of the dielectric resistor plate material during the preliminary operation. The top and bottom portions of the fixtures in FIGS. 4 to 6 are also provided, with insulating material i covers 3b and 31, such as mica, as indicated With respect to the embodiments shown in FIGS. 1 and 3.

in embodiment shown in N68. 7 and 8, it will be noted that each fixture plate 32 is provided extensions or pins 33 so as to hold each plate 32 individually on the plate 34 without requiring spacers. Said resistor plates 32 are notched at spaced intervals 35 to perm-it mounting on the pins 3 3 of plate 34.

The operation in connection with the preparation of flat resistor plates is the same as the operation described herein above with respect to the tubular resistors. It is to be noted that the end portion of either the flat or tubular members can be precovered or coated by means of electrical conductors and adapted for immediate use after the internal portion of the tube or one of the fiat surfaces of the plate has been coated and already resistance determined. In the modifications shown in FIGS. 4 to 8 the fixtures may be hinged or connected together so as to obtain a polygonal section, in which case, there is also provided a central filament 36 besides auxiliary filaments 37 all supported at the top thereof and connected to a common source of electrical current.

From the foregoing description, taken in connection with the accompanying drawings, it will be noted that, by my invention, 1 provide a resistor having a film of nickel-chrome alloy deposited on the inner Wall of a glazed or unglazed ceramic, glass or similar type of tube on which a metal terminal material has been baked or otherwise deposited at each end. Furthermore, there is provided a ceramic tube in which grooves have been out either in the form of a helix having metal terminals deposited at each end of the tube, and a metallic film is deposited on the inside of the tube so as to form a resistance path between the metal terminals. The metal film may be removed from the inside diameter of the grooves or threads so as to form threads of resistance material paths between the metal terminals in the second, said removal being dependent upon the amount of resistance desired or needed, but approximately the same amount of material will always be removed from all parts.

While preferred embodiments of my invention have been illustrated and described, it is to be understood that modifications as to form, arrangement of parts and use of materials may be made without departing from the spirit and scope of the invention as claimed herein.

I claim:

l. A method of making metal film resistors comprising arranging a plurality of dielectric material selected from the group consisting of glazed material, Alundurn, porcelain, glass or the like, having internally threaded cylindrical shape, arranging said units in tandem, providing spacers, between each of the units arranged in tandem, assembling said units while in tandem as a whole and arranging the same in an evacuating chamber, subjecting the assembled whole to the action of outgassing, then subjecting the assembled whole to the action of vacuum in said chamber in a range from 10- to 10-" mm. of Hg, sublimating onto the exposed surface of said dielectric material in the vacuum chamber an alloy material from a coaxial filament of incandescent alloy material, selected from the group consisting of chromium, copper and nickel for a period of 5 minutes to 5 hours at a temperature of C. to 450 C. allowing the Vacuum chamber to cool while the vacuum action therein and heating of the filament have been discontinued, removing the whole unit from the vacuum chamber, and then reheating in open air so as to stabilize the unit and grind ing the lands to increase resistance to a predetermined value.

2. A method of making metal film resistors on a mass production basis comprising arranging a plurality of units of insulated dielectric material having metallic terminals fired onto each end of said material, arranging said ma-.

terial in tandem, forming intermediate spaced areas between each of said uni-ts of material, supporting the arrangement of each unit of said material, whereby they remain in consecutive arrangement relatively to each other, passing an alloy filament along the length adjacent the proximate surface of each of said units, placing the re sultant assembly of said units and the filament in a vacuum chamber, connecting said filament to a source of variable electrical power, securing said filament to prevent sagging of the same when heated, removing the air from the vacuum chamber in a range from to 10- mm. Hg and then heating the filament [and the units in the vacuum chamber to a temperature under the sublimation temperature of the filament so as to outgas said filament and the units and the gas in the chamber, heating the filament by passing electric current therethrough to a point sufiiciently high to sublimate the components of the filament whereby the components of the filament pass from the filament onto the proximate surface of each of said units, obtaining the desired amount of deposit of alloy metals on the units, discontinuing the vacuum operation in the chamber, allowing the contents of the chamber to cool, removing the contents of the chamber, and heat treating the unit at elevated temperature in air to stabilize said units, sorting said units, checking and automatically indicating the resistance value thereof, while adjusting the resistance of each of the units by abrasion to obtain a desired ohmic value for the individual unit; and finally capping the units and coating the same.

3. A method of making metallic film resistors comprising assembling a plurality of superimposed spaced blanks made of a material selected from the group consisting of glass, porcelain and Alundum, in a supporting fixture arranged in cylindrical array,

an interior surface of each blank being exposed to the coating action of an electroconducting filament of an alloy material selected from the group consisting of copper, nickel and chromium extending adjacent the inner face of each blank,

placing the resultant assembly in an evacuating chamber,

evacuating the chamber to at least 10* mm. Hg,

heating the assembly to a temperature sutlicient to outgas the same at said vacuum,

passing an electric current through the filament, while continuing to apply a vacuum to said chamber to reduce the same to a high vacuum,

the magnitude of the current passing through the filament being sufficient to cause the metal of the filament to sublime onto the adjacent surface of the blanks, and

finally discontinuing the current in the filament.

References Cited in the file of this patent UNITED STATES PATENTS 929,017 Reynard July 27, 1909 1,859,112 Silberstein May 17, 1932 2,403,199 Swope July 2, 1946 2,411,715 Dimmick Nov. 26, 1946 2,416,347 Rector Feb. 25, 1947 2,453,801 Mattern Nov. '16, 1948 2,469,100 Andrus May 3, 1949 2,586,752 Weber et a1 Feb. 19, 1952 2,792,620 Koring May 21, 1957 2,917,814 Ruckelshaus Dec. 22, 1959 2,962,393 Ruckelshaus Nov. 29, 1960 

1. A METHOD OF MAKING METAL FILM RESISTORS COMPRISING ARRANGING A PLURALITY OF DIELECTRIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF GLAZED MATERIAL, ALUNDUM, PORCELAIN, GLASS OR THE LIKE, HAVING INTERNALLY THREADED CYLINERICAL SHAPE, ARRANGING SAID UNITS IN TANDEM, PROVIDING SPACERS, BETWEEN EACH OF THE UNITS ARRANGED IN TANDEM, ASSEMBLING SAID UNITS WHILE IN TANDEN AS A WHOLE AND ARRANGING THE SAME IN AN EVACUATING CHAMBER, SUBJECTING THE ASSEMBLED WHOLE TO THE ACTION OF OUTGASSING, THEN SUBJECTING THE ASSEMBLED WHOLE TO THE ACTION OF VACUUM IN SAID CHAMBER IN A RANGE FROM 10-3 TO 10-7 MM. OF HG SUBLIMATING ONTO THE EXPOSED SURFACE OF SAID DIELECTRIC MATERIAL IN THE VACUUM CHAMBRER AN ALLOY MATERIAL FROM A COAXIAL FILAMENT OF INCADESCENT ALLOY MATERIAL, SELECTED FROM THE GROUP CONSISTING OF CHROMIUM, COPPER AND NICKEL FOR A PERIOD OF 5 MINUTES TO 5 HOURS AT A TEMPERATURE OF 150*C. TO 450*C. ALLOWING THE VACUUM CHAMBER TO COOL WHILE THE VACUUM ACTION THEREIN AND HEATING OF THE FILAMENT HAVE BEEN DISCONTINUED, REMOVING THE WHOLE UNIT FROM THE VACUUM CHAMBER, AND THEN REHEATING IN OPEN AIR SO AS TO STABILIZE THE UNIT AND GRINDING THE LANDS TO INCREASE RESISTANCE TO A PREDETERMINED VALUE. 